In the preparation of a vaccine great care must be used in heating so that the organisms are killed, but the _antigens_ are not destroyed. Many of the enzymes present in bacteria, especially the proteolytic ones, are not any more sensitive to heat than are the antigens, hence are not destroyed entirely. Therefore a vaccine kept in stock for a long time gradually has some of its antigens destroyed by the uninjured enzymes present with them, and so loses in potency. Therefore in treating a given infection it is well to make up a vaccine from the lesion, use three or four doses and if more are necessary make up a new vaccine. If the above statements are borne in mind and vaccines are made and administered accordingly, the author is well satisfied that much better results will be secured. In accordance with the theory on which the use of vaccines is based, _i.e._, that they stimulate the body cells to produce immunizing antibodies, it is clear that they are especially suitable in those infections in which the process is _localized_ and should not be of much value in _general_ infections. In the latter case the cells of the body are stimulated to produce antibodies by the circulating organisms, probably nearly to their limit, hence the introduction of more of the same organisms, capable of stimulating though dead, is apt to overtax the cells and do more harm than good. It is not possible to tell accurately when this limit is reached, but the clinical symptoms are a guide. If vaccines are used at all in general infections they should be given in the early stages and in small doses at first with close watch as to the effect. In localized infections only the cells in the immediate neighborhood are much stimulated, hence the introduction of a vaccine calls to their aid cells in the body generally, and much more of the resulting antibodies are carried to the lesion in question. Manifestly surgical procedures such as incision, drainage, washing away of dead and necrotic tissue with normal saline solution, not necessarily antiseptics, will aid the antibodies in their action and are to be recommended where indicated.